Abstract

When DL-tryptophan-2-C14 was incubated with washed cells or cell-free preparations of Pseudomonas savastanoi, two radioactive metabolites were formed. One was identified as indoleacetamide and the second, indoleacetic acid. The amount of indoleacetamide in the reaction mixture increased rapidly during the early stages of incubation; it reached a peak after 15 minutes and declined steadily there-after. Indoleacetic acid, on the other hand, accumulated slowly throughout the incubation period. Cell-free preparations preferentially utilize the L-isomer of tryptophan for the synthesis of indoleacetamide and indoleacetic acid. The results of these experiments suggest, therefore, that P. savastanoi synthesizes indoleacetic acid by the following reactions: L-tryptophan→ indoleacetamide→indoleacetic acid.